1. Field of the Invention
The present invention relates to a metal frame for eyeglasses.
2. Related Arts
A variety of frames have rim-to-temple-joint means on their opposite sides for foldably fixing two temples to the opposite sides of the frame. When one wears the eyeglasses on one's face, the ends of the opposite temples of the eyeglasses are applied to the opposite sides of the head to prevent the eyeglasses from displacing from correct position. If the temples become rickety at their hinges, the eyeglasses cannot fit on one's face, and is apt to be unstable in position.
Usually the opposite temples are yieldingly bent more or less when the eyeglasses are worn on one's face, thereby positively fitting on the head as a counter action. Ceaseless application of pressure on the head, however, will cause unpleasing feeling or discomfort of the head. In an attempt to settle this problem a conventional frame uses spring-installed hinges for connecting temples to its opposite sides. The spring-installed hinge permits the folding and unfolding of an associated temple. It permits the temple to be opened somewhat wider than the normal opening position relative to the front by compressing the spring, which is installed in the hinge structure. Thus, the temples are pushed against the opposite sides of the head at controlled moderate pressure, thus assuring that the eyeglasses are put in correct position all the time.
Advantageously when the temples are opened by force, the spring-installed hinge can be so changed in shape as to prevent any deformation of the front frame, which otherwise, would be caused, and sometimes would lead to lens breakage or the slipping-off of lenses from the front. The spring-installed hinge, however, is complicated in structure, and accordingly the cost involved for manufacturing is high. Also, disadvantageously the spring-installed hinge is easy to break, and the joint size is apt to be large, giving unpleasing sight in appearance.
Referring to FIG. 8, a conventional spring-installed hinge comprises a stationary part B soldered to one or the other joint piece A of the front and a slidable part C having a coiled spring E installed in its cavity. The slidable part C is slidably fitted in a guide slot, which is made in the temple D. The coiled spring E has a headed core rod and loosely wound around the shank of the headed core rod. The head I of the core rod is fixed to its end, and the head I confronts a detent piece G having an engagement projection H on its distal bottom edge. The detent piece G is laid on the temple D with its engagement projection H loosely caught by a groove F, which is made on the temple D just behind the head I of the headed core rod. When the temple D is opened wider beyond the normal opening position, the coiled spring E is compressed so that the head I may abut the detent piece G, thereby applying a counter force to the temple D in the direction in which the temple D returns to the original or normal opening position.
The spring-installed hinge is complicated in structure, and is expensive. Once the spring-installed hinge has been broken, it cannot be repaired with ease. The coiled spring E and its core rod are pushed in the cavity of the slidable part C, and the spring-and-core assembly is retained there in the cavity by allowing the head I to abut the detent piece G. With this arrangement the detent piece G and the coiled spring E cannot be removed. The bottom projection H of the detent piece G is put in the groove F, and the detent piece G is confined in the slidable part C while being pushed by the headed core rod under the influence of coiled spring E, so that the detent piece G may be fixedly held in position. Thus, the detent piece G cannot be removed from the slidable part C with ease, preventing the disassembling and mending of the resilient hinge structure once it has been broken.
The spring-installed hinges permit the opposite temples to be opened wider beyond the normal opening position, thereby causing the opposite temples to be applied to the opposite sides of the head under the resilient influence, thus putting the eyeglasses stably in position. The spring-installed hinges permit the temples to be opened outward in a plane containing two opposite hinges, not permitting the temples to be changed vertically in position. Therefore, the spring-installed hinges cannot allow the temples to be separately changed in vertical position to fit on the head, which is asymmetrical more or less, as for instance, there are two ears, one on each side of the head, at somewhat different levels. As a result one is liable to feel discomfort of the head. Eyeglasses are so adjusted as to fit one's head at an eyeglasses shop. The eyeglasses thus adjusted, however, are liable to reduce its fitness on the head less and less with time.